As you may know, AppSSO is certainly a multi-layered use-case and it might be tricky for us to diagnose in a forum thread here, so I'd recommend opening a service request with Support to help track down the issue. For RemoteApp, PAM leverages Microsoft Remote Desktop Role Services (RDS) and perhaps there has been some sort of misconfiguration there or perhaps a missing missing module or PAM is configured to point to an incorrect RD Connection Broker server or some incorrect Collection Name, etc. Those are some possible causes that I can think of at this time.